(1) Field of the Invention
The present invention relates to a process for the preparation of a coated plastic container. More particularly, the present invention relates to a process for the preparation of a coated plastic container in which the adhesion, gas barrier property, strength and chemical resistance can be improved by crystallizing a coating layer of a vinylidene chloride copolymer formed on a plastic container substrate.
(2) Description of the Prior Art
Plastic bottles prepared by melt-extruding and hollow-molding (blow-molding) thermoplastic plastics such as polyolefins are used in various fields instead of glass bottles because the plastic bottles have a lighter weight and a better shock resistance than the glass bottles.
General-purpose plastics such as polyolefins are excellent in the moisture resistance and sanitary characteristics, but the oxygen permeability coefficient is relatively high and in bottles of these plastics, permeation of oxygen through bottle walls is not negligible. Accordingly, bottles of general-purpose plastics are not suitable as vessels for preserving foods for a long time or as vessels for cosmetics and the like where a high flavor-retaining property is required.
As bottles in which this defect is overcome, there have been developed and proposed plastic bottles having a wall structure excellent in the oxygen barrier property. Among melt-extrudable thermoplastic resins which are now available, a saponified ethylene/vinyl acetate copolymer (ethylene/vinyl alcohol copolymer) is most excellent in the oxygen barrier property. However, this saponified copolymer is inferior in the moisture resistance, that is, the steam barrier property, and in this saponified copolymer, the oxygen permeability coefficient tends to increase as increase of the humidity. Accordingly, when this saponified copolymer is actually used for formation of plastic bottles, it is necessary to adopt a troublesome molding method in which this saponified copolymer is sandwiched by moisture-resistant resins such as polyolefins and the resulting laminate is fed to the molding step to form a multi-layer laminate bottle.